[openssl-users] PKCS7_sign conflict with PKCS7_decrypt?

Tue Jul 26 15:28:47 UTC 2016

Steve -- thanks, but I don't think I was clear enough. 

I am trying to get back the signed content, but when I call PKCS7_decrpyt()
I get back an empty buffer.  Is this my flawed understanding of
PKCS7_sign().  Is there some other way to get back the original signed
content that I'm missing?

>From the NOTES section of PKCS7_sign():

	The data being signed is included in the PKCS7 structure, unless 
	PKCS7_DETACHED is set in which case it is omitted

> -----Original Message-----
> From: openssl-users [mailto:openssl-users-bounces at openssl.org] On
> Behalf Of Dr. Stephen Henson
> Sent: Tuesday, July 26, 2016 11:22 AM
> To: openssl-users at openssl.org
> Subject: Re: [openssl-users] PKCS7_sign conflict with PKCS7_decrypt?
> 
> On Tue, Jul 26, 2016, Jim Carroll wrote:
> 
> > Running into trouble -- any attempt to PKCS7_decrypt() S/MIME content
> that
> > was created with PKCS7_sign()+PKCS7_encrypt() yields an empty result
> set.  I
> > have the distinct impression I'm doing something dumb -- but several
> days of
> > debugging I'm completely stuck.
> >
> > I've created an MVCE and included it below. The code was built and
> run on
> > Windows 8.1 Pro, Visual C++ 2008 Express, using OpenSSL 1.1.0-pre6-
> dev
> > (32-bit build).
> >
> > Interesting point -- If I remove the PKCS7_sign() code, I have no
> problem
> > encrypting and decrypting the content. I strongly suspect my issue
> has
> > something todo with S/MIME headers interfering with encryption or
> > decryption.  But that theory would suggest there's a bug in OpenSSL's
> S/MIME
> > handling. I find that hard to swallow -- more likely I'm missing some
> sort
> > of required flag.
> >
> 
> What you're doing is sign followed by encrypt which gives a signed
> messsage
> within an encrypted one.
> 
> Then you just decrypt which ends up giving you the signed content back.
> So if
> you want to process that you have to verify it first.
> 
> Note there is a big in the current master which breaks CMS/PKCS#7
> (overlapping
> buffers check) so you'll have to either try an earlier version or wait
> for it
> to be fixed.
> 
> Steve.
> --
> Dr Stephen N. Henson. OpenSSL project core developer.
> Commercial tech support now available see: http://www.openssl.org
> --
> openssl-users mailing list
> To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users

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